1. Field of the Invention
The present invention pertains generally to the treatment of disordered breathing, and more particularly, to selecting a device adapted to treat a patient who suffers from disordered breathing.
2. Description of the Related Art
It is well known that many individuals suffer from disordered breathing during sleep. Obstructive sleep apnea (OSA), which affects millions of people throughout the world, is a common example of such disordered breathing. OSA is a condition in which sleep is repeatedly interrupted by an inability to breathe. This inability to breathe is typically caused by intermittent obstruction of a person's airway. Obstruction of the airway is believed to be due, at least in part, to a general relaxation of the muscles which stabilize the upper airway segment. When these muscles relax, the surrounding tissues collapse thereby obstructing the airway.
Those afflicted with OSA experience sleep fragmentation and intermittent cessation of ventilation during sleep with potentially severe degrees of oxyhemoglobin desaturation. These symptoms may be translated clinically into extreme daytime sleepiness, cardiac arrhythmias, pulmonary-artery hypertension, congestive heart failure and/or cognitive dysfunction. Other consequences of OSA include right ventricular dysfunction, carbon dioxide retention during sleep, as well as wakefulness, and continuous reduced arterial oxygen tension. Sleep apnea sufferers may be at risk for excessive mortality from these factors as well as by an elevated risk for accidents while driving and/or operating potentially dangerous equipment.
A person may suffer from the adverse effects discussed above even where only partial obstruction of the airway occurs. Partial obstruction of the airway typically results in shallow breathing referred to as a hypopnea. Other types of disordered breathing include upper airway resistance syndrome (UARS) and vibration of the airway, such as vibration of the pharyngeal wall, commonly referred to as snoring. It is also known that snoring can accompany closure of the airway leading to UARS, hypopnea, or apnea. Thus, snoring serves as an indicator that the patient is experiencing abnormal breathing.
Milder cases of disordered breathing may be treated using an oral appliance such as a mandibular advancement device (MAD). A MAD is generally structured to pull a patient's lower jaw (mandible) forward relative to their upper jaw (maxilla), which in turn, opens the patient's airway.
More severe cases of disordered breathing may be treated by applying a continuous positive air pressure (CPAP) to the patient's airway. This positive pressure effectively “splints” the airway, thereby maintaining an open passage to the lungs. It is also known to provide a positive pressure therapy in which the pressure of gas delivered to the patient varies with the patient's breathing cycle, or varies with the patient's effort, to increase the comfort to the patient. One such pressure support technique is referred to as bi-level pressure support (e.g., BiPAP® bi-level pressure support), in which the inspiratory positive airway pressure (IPAP) delivered to the patient is higher than the expiratory positive airway pressure (EPAP) delivered to the patient. Other pressure support therapies and/or ventilation therapies are known and employed for the treatment of disordered breathing.
Pressure support and ventilation therapies may be non-invasively delivered to the patient. A patient interface device, generally placed on the face of a patient, facilitates the delivery of a flow of breathing gas from a pressure/flow generating device (e.g., a ventilator, pressure support device, etc.) to the airway of the patient. Patient interface devices include nasal prongs, nasal masks, full nasal/oral masks, and total face masks, among others. The pressure of the flow of breathing gas delivered to the patient is generally derived through a titration process administered by a sleep technician. The pressure at which the flow of breathing gas is delivered, herein referred to as the “therapeutic pressure”, is generally between 4 cm H2O and 40 cm H2O, although other pressures may be employed.
Patient comfort is maximized by providing the flow of breathing gas at a minimum effective therapeutic pressure (i.e., at the minimum pressure necessary to keep the patient's airway open). Furthermore, adverse conditions (for example and without limitation, mask leakage, skin breakdown caused by mask over-tightening, and acrophage) may be avoided at lower therapeutic pressures. Improved patient compliance with the prescribed therapy is achieved by increasing patient comfort and decreasing the likelihood that the patient experiences adverse conditions.
The device selected to treat disordered breathing (e.g., an oral appliance or a patient interface device) is an important component for ensuring patient compliance and adequate treatment outcomes. For example, the type and/or style of the patient interface device selected is an important component for insuring patient compliance and for insuring that the minimum effective therapeutic pressure is prescribed to the patient. The flow of gas supplied to a patient encounters resistance associated with, for instance, the patient's nasal cavity and/or oral cavity. These resistances may vary from patient to patient. A patient suffering from a number of intranasal pathological conditions (such as and without limitation, deviated septum, polyps, hypertrophic turbinates and spurs, trauma, congenital problems, sinus infections, etc.) may have a high nasal resistance. If a nasal mask is the type selected for such a patient, the minimum effective therapeutic pressure that must be prescribed to overcome the patient's elevated nasal resistance may be relatively high. However, if a nasal/oral mask is the type selected, the minimum effective therapeutic pressure may be relatively low because the patient will also be able to breathe through his/her mouth, thus bypassing the elevated nasal resistance. Prescribing a lower minimum effective therapeutic pressure increases the likelihood that the patient will comply with his/her therapy.
Applicant is unaware of any prior art methods in which one or more characteristics of the patient's airway (and/or the effects on breathing caused by these characteristics) are considered during the selection of an appropriate device for treating disordered breathing.
Accordingly, a need exists for a method of selecting the appropriate device for treating disordered breathing and which overcomes these and other problems associated with known methods.